The heart of the telescope is a 94.5 inch-diameter (2.4-meter) mirror. It is the smoothest optical mirror ever polished, with a surface tolerance of one-millionth of an inch. It is made of fused silica glass and weighs about 1,800 pounds.

Outside the blurring effects of Earth's turbulent atmosphere, the telescope can resolve astronomical objects with an angular size of 0.05 arc seconds, which is like seeing a pair of fireflies in Tokyo from Maryland. This razor-sharp vision is 10 to 20 times better than ground-based telescopes

Because it is outside our atmosphere, the telescope can view astronomical objects across a broad swath of the electromagnetic spectrum, from ultraviolet light, to visible, to near-infrared wavelengths.